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Mellon  Institute  of  Industrial  Research  and  School  of 
Specific  Industries 

Smoke  Investigation  Bulletin  No«  7 


The  Effect  of  the  Soot  in  Smoke 
on  Vegetation 


By 

J.  F.  CLEVENGER,  M.  A. 


Univefsity  of  Pittsburgh 
Pittsburgh,  Pa. 

J9J3 


nd  School  of 

Director. 

liate  Director. 

and  Chemist. 

, Attorney. 

)cli.  Engineer. 
..Physician. 
OF  CALIFORNIA         : Botanist 


LIBRARY 
THE  UNIVERSITY 


SANTA  BARBARA 


PRESENTED  BY 

FRED  E.  CLEMENTS 


Mellon 

Robert  ] 
Raymoni 

Kaymon< 
Joseph  A 

A.  B.  Be 
VV.  W.  I 
J.  F.  Cle 

B.  A.  Co 
E.  W.  D 
S.  R.  Ha 
W.  L.  H 
Richard 

C.  T.  Ini 
Richard 

H.  H.  Kimball,  Ph.D Meteorologist. 

Oskar  Klotz,  M.D.,  CM Physician. 

E.  B.  Lee Architect. 

C.  H.  Marcy,  A.B Bacteriologist 

O.  R.  McBride,  B.S Mech.  Engineer. 

E.  H.  McClelland,  Ph.B Bibliographer. 

R.  T.  Miller,  Jr.,  A.B.,  M.D Surgeon. 

A.  F.  Nesbit,  B.S.,  A.M Elec.  Engineer. 

J.  J.  O'Connor,  Jr.,  A.B Economist. 

K.  K.  Stevens,  B.S Chemist 

A.  A.  Straub,  M.E Mech.  Engineer. 

Carlton  Strong Architect 

W.  W.  Strong,  Ph.D Physicist 

J.  E.  Wallace  Wallin,  Ph.D Psychologist 

W.  C.  White,  M.D Physician. 

Ruth  E.  Gilchrist Secretary. 


...Physician. 
...Physician. 
...Physician. 
...Physician. 
....Architect 
....Architect 
....Architect 


J  v  «J  k./       V  ;  ;„M  4  ^.  4\  T 

Y  T7459 


Mellon  Institute  of  Industrial  Research  and  School  of 
Specific  Industries 

Smoke  Investigation  .  Bulletin  No^  7 


The  Effect  of  the  Soot  in  Smoke 
on  Vegetation 


By 

J.  F.  CLEVENGER,  M.  A. 


University  of  Pittsburgh 
Pittsburgh,  Pa. 

J9J3 


Digitized  by  the  Internet  Archive 

in  2007  with  funding  from 

IVIicrosoft  Corporation 


http://www.archive.org/details/effectofsootinsmOOcleviala 


Note  by  the  Editor 

The  investigation  described  in  this  bulletin  was  under- 
taken by  the  Botanical  Department  of  the  Pennsylvania 
State  College  in  oo-operation  with  the  Department  of  In- 
dustrial Research  of  the  University  of  Pittsburgh,  now 
known  as  the  Mellon  Institute  of  the  University  of  Pitts- 
burgh. The  investigation  was  begun  in  March,  1912,  and 
continued  about  one  year  and  a  half. 

The  Mellon  Institute  desires  to  express  its  apprecia- 
tion of  the  co-operation  of  State  College  and  to  thank  Mr. 
J.  F.  Clevenger,  who  carried  on  the  investigation. 

John  O'Connor,  Jk. 


Table  of  Contents 


Introduction 5 

Historical  review 7 

Observations  and  experiments 10 

The  regions  selected 13 

Controlled  field  experiments 17 

Analyses  of  soot 18 

Experiments  in  nursery  and  greenhouse 18 

Experiments  with  pea  seedlings 20 

Soot  fall  21 

General  Considerations  22 

Conclusions 24 

Bibliography  of  references  cited  in  text 26 


Introduction 

The  present  paper  attempts  to  determine,  primarily, 
tlie  effect  of  the  soot  in  smoke  and  included  materials  upon 
plants.  General  observations  have  been  made  by  the  writer 
in  the  following  localities:  certain  of  the  public  parks  in 
Chicago;  in  Pittsburgh  and  vicinity;  along  the  railroad 
between  Pittsburgh  and  Tyrone ;  and  at  State  College  and 
vicinity.  Specific  observations  by  means  of  controlled 
laboratory  experiments  were  made  at  State  College,  Penn- 
sylvania. While  the  observations  have  not  been  so  numer- 
ous as  might  be  desirable,  yet  the  writer  feels  that  they 
will  warrant  the  conclusions  drawn.  He  has  the  feeling 
that  the  data  obtained  have  been  somewhat  meager  owing 
to  the  fact  that  the  investigation  has  not  been  prolonged 
over  a  sufficiently  long  period  of  time. 


Fl^.3.  Oak. 


f^ia.  ^.  A/ine  Mile  Run 

Plate  Z 

PLATE    I. 

Fig.  3.  Shows  a  dead  oak  on  the  hillside  of  Munhall  Run  about  one  mile 
from    the    mills    at    Homestead,    a    common    sight. 

Fig.  4.  Shows  a  view  of  the  hillside  and  hilltop  near  Nine  Mile  Run  across 
the  river  from  the  mills  in  Homestead.  This  shows  the  almost  complete  de- 
struction  of   the   trees   at   this   place. 


F'lQ  J"  ULmus 


fiQ.  6.  ULmus . 


Plate  R 


PLATE    II. 


Fig.  5.  Cross  sections  of  an  Ulmus  (American  elm)  growing  in  region  6  of 
the  Aliquippa  district  near  the  mill  and  showing  the  distinct  effect  of  smoke 
and    gases. 

Fig.  6.  Cross  sections  of  an  Ulmus  (American  elm)  growing  on  the  hillside 
tu  region  5,  Aliquippa  district.  Shows  a  tendency  toward  a  narrowing  of  rings. 
Kvldently   effected   by   the  smoke   and   gases   from   the   trains. 


THE  EFFECT  OF  SOOT  ON  VEGETATION. 


Historical  Review 

Various  phases  of  this  subject  have  been  studied  from 
time  to  time  by  different  investigators,  the  most  of  whom 
agree  on  many  of  the  more  important  points.  The  effect 
of  various  gases  upon  plants  must  be  considered  in  con- 
nection with  the  effect  of  soot  because  with  the  soot  in 
smoke  there  are  always  associated  various  gases,  as 
Crowther  and  Ruston  (5)  have  shown.  Crocker,  Knight 
and  Kose  (4,  9,  10,  11)  by  their  several  and  conjoint  inves- 
tigations and  discussions  of  literature  have  established  be- 
yond reasonable  doubt  the  high  toxicity  of  certain  gases 
to  plants,  especially  ethylene,  and  the  injury  done  by 
greater  quantities  of  other  gases.  Their  first  paper  deals 
with  illuminating  gas  and  its  constituents,  while  a  later 
paper  deals  with  the  effect  of  smoke,  and  particularly 
tobacco  smoke,  upon  etiolated  pea  seedlings.  Although 
the  various  responses  which  they  obtained  were,  for  the 
most  part,  with  etiolated  seedlings,  yet  information  con- 
cerning the  effect  upon  normal  plants  is  not  lacking,  as 
is  evidenced  by  the  almost  complete  destruction  of  certain 
plants  by  acute  poisoning  in  a  greenhouse  during  the  fumi- 
gation with  tobacco  smoke.  Buckhout  (2)  has  pointed 
out  the  destruction  of  vegetation  in  the  neighborhood  of 
the  chemical  works  at  Natrona,  Pennsylvania.  This  he 
attributes  to  the  Sulphur  trioxide  (SO3)  and  sulphur 
dioxide  (SO2)  fumes.  Haywood  (8)  observed  similar 
effects  in  the  neighborhood  about  the  smelters  near  Red- 
ding, California.  He  went  further,  however,  and  obtained 
evidence  bearing  on  the  specific  injury  suffered  by  plants 
from  SO2  and  SOs  fumes.  He  demonstrated  that  these 
gases  were  responsible  for  at  least  a  major  part  of  the 
injury  suffered  by  the  plants  in  the  vicinity.  Widstoe  (8) 
found  that  SO2  in  small  quantities  acting  for  a  long  time 
is  toxic  to  plants.  Peirce  (14)  believes  that  the  cement 
factories  in  the  San  Bernardino  Valley  of  Southern  Cal- 


8  THE  SMOKE  INVESTIGATION 

ifomia  caused  a  decrease  in  crop  production  by  covering 
the  leaves  with  an  incrustation  of  dust  and  thereby  inter- 
fering with  the  energy  relations.  Parish  (15)  estimated 
that  the  lemon  crop  in  the  vicinity  of  the  Stower  Moun- 
tains was  cut  down  one-fourth  on  account  of  the  presence 
of  a  large  cement  factory.  He  points  out  that  while  the 
stomata  are  not  clogged  with  dust,  nevertheless  this  inter- 
feres with  photosynthesis.  Ruston  (17)  found  in  the 
vicinity  of  Leeds,  England,  that  a  black  adhesive  film 
covers  the  leaves  of  many  tress,  particularly  evergreens, 
and  thereby  interferes  with  photosynthesis.  He  further 
reports  that  eighty  per  cent,  of  the  Fir  leaves  had  their 
stomata  clogged.  Crowther  and  Ruston  (5)  found  that 
impurities  in  the  air  were  present  in  large  quantities  in 
and  a'bout  industrial  centers.  They  found  that  the  sus- 
pended matter  brought  down  by  rains  has  an  injurious 
effect  upon  vegetation,  by  direct  action  on  the  leaves ;  and 
indirectly  by  reducing  the  activity  not  only  of  the  neces- 
sary ammoniacal  fermentation  of  the  soil  humus,  but  even 
more  of  the  beneficial  nitrifying  and  nitrogen-fixing  organ- 
isms in  the  soil.  Gatin  (6,  7)  found  that  various  tar  prod- 
ucts used  in  road  pavements  were  injurious  to  vegetation 
and  that  the  effects  might  be  produced  by  the  action  of 
the  various  gases ;  and  by  the  action  of  the  dust.  He  found 
that  the  fumes  of  tar  brought  about  the  alteration  in  the 
size  and  num'ber  of  layers  in  the  cortex  and  other  regions 
of  the  stem,  and  the  transformation  of  doubly  compound 
leaves  into  singly  compound  leaves.  He  also  reported  the 
disappearance  of  starch  and  the  formation  of  cork  in  leaf 
organs  and  stems.  Molisch  (13,  14)  found  that  tobacco 
smoke  had  a  marked  injurious  effect  upon  micro-organisms. 
Cohen  and  Ruston  (3)  brought  together  the  records  of 
their  observations  which  had  been  carried  on  at  intervals 
during  the  past  twenty  years.  They  gave  data  concern- 
ing the  composition  of  soot  collected  from  the  bottom  and 
top  of  chimneys  of  dwellings  as  well  as  from  the  boilers 
of  a  number  of  factories,  finding,  of  course,  that  the  soot 
varies  considerably,  depending  upon  the  conditions  under 
which  the  coal  was  burned.    Thev  also  obtained  data  rela- 


THE  EFFECT  OF  SOOT  ON  VEGETATION.  9 

tive  to  the  amounts  of  solid  impurities  found  in  the  air 
at  a  number  of  stations.  They  attributed  the  observed 
injury  on  vegetation  to  the  blocking  up  of  stomata,  thus 
impeding  the  process  of  transpiration;  to  the  coating  of 
the  leaf,  thereby  reducing  the  intensity  of  sunlight  and 
at  the  same  time  affecting  the  diffusion  of  caribou  dioxide 
into  the  leaf;  and  to  the  corrosive  effect  of  the  acid  it  con- 
tain«.  The  injury  took  the  form  of  a  general  reduction 
in  the  size  of  the  leaves  and  plants.  It  was  also  seen  in 
the  narrowing  of  the  annual  rings  in  trees. 


10  THE  SMOKE  INVESTIGATION 


Observations  and  Experiments 

Aside  from  the  general  observations  and  experiments 
which  were  carried  on,  circular  letters  were  sent  out  to 
various  florists  and  gardeners  in  and  near  Pittsburgh. 
Following  is  a  sample  of  the  inquiries  in  the  circular  let- 
ters and  of  the  replies  received : 

1.  Date  of  reply :    A.   About  July,  1912. 

2.  State  your  general  business  (such  as  Florist,  Gard- 
ener, etc.)  : 

A.  About  thirty  replies  were  received,  these  being 
almost  equally  distributed  between  florists  and  gardeners. 

3.  What  plants  native  to  Pittsburgh  and  vicinity  do  you 
consider  grow  poorly  or  not  at  all,  because  of  the  smoke, 
soot  and  gases? 

A.  Evergreens,  Sugar  Maples,  and  other  plants  in 
more  or  less  impoverished  condition. 

4.  What  plants  introduced  into  Pittsburgh  and  vicinity 
thrive  poorly  or  not  at  all,  because  of  the  injurious  effects 
of  smoke  and  gases? 

A.     Evergreen  trees.  Spiraea  and  White  Oak. 

5.  What  plants  native  to  Pittsburgh  and  vicinity  thrive 
well  in  spite  of  the  smoke  and  gases? 

A.     Rhus,  Salix,  and  grasses. 

6.  What  plants  introduced  into  Pittsburgh  and  vicinity 
do  well  in  spite  of  the  smoke  and  gases? 

A.  Ailanthus,  Norway  Maples,  Platanus  occidentalis, 
and  Syringa. 

7.  What  is  the  character  of  the  injury  done  to  your  plants, 
or  any  plant  w^hich  you  have  oibserved? 

A.  Stomata  stopped,  buds  and  foliage  have  the  ap- 
pearance of  being  subjected  to  intense  heat  or  fire,  and 
dying  of  trees  from  the  top  down. 

8.  How  much  of  this  injury  do  you  attribute  to  smoke, 
and  how  much  to  gas  and  other  causes? 


THE  EFFECT  OF  SOOT  ON  VEGETATION.  11 

A.  The  general  opinion  is  that  the  injury  is  due  col- 
lectively to  the  smoke  and  gases. 

9.     Have  you  lived  in  other  places  where  these  conditions 
of  smoke  and  gas  do  not  exist? 

A.     They  usually  had. 

If  so,  state  where,  when,  and  how  long,  and  give  the 
general  conditions  which  existed  at  this  place. 

A.  Most  had  lived  in  other  localities  where  they  did 
not  have  to  contend  with  smoke  and  gases. 

The  writer's  oibservations  in  the  main  confirm  these 
replies.  The  specific  causes  for  these  injuries  may  not  be 
so  easily  fixed,  for  it  must  be  recognized  that  there  are 
a  number  of  factors  which  must  be  considered,  such  as 
rainfall,  temperature,  humidity,  transpiration,  various 
soots  and  gases  liberated  from  chimneys  and  smokestacks, 
and  dust. 

In  order  to  show  that  plants  are  injured  by  various 
by-products  given  off  into  the  air  by  the  industrial  estab- 
lishments, specific  locations  were  selected  and  kept  under 
constant  observation  during  the  summer  of  1912  and  cer- 
tain data,  which  will  be  presented  later,  were  obtained. 

To  get  some  general  notion  of  the  climatic  conditions 
of  these  regions,  atmometer  cups  of  the  Livingston  type 
were  employed  and  weekly  readings  were  made.  In  addi- 
tion to  this,  The  Annual  Meteorological  Summary  of  Pitts- 
l^urgh  for  the  past  four  years  was  consulted.  The  atmom- 
eter readings  are  given  in  the  form  of  curves.  The  amount 
of  evaporation  is  given  in  cubic  centimeters  per  25  square 
centimeters  of  evaporating  area.  The  time  intervals  are 
approximately  seven  days  (Fig.  1). 

By  referring  to  Figure  1,  we  note,  in  the  first  place, 
that  the  curves  for  the  most  part  run  low,  indicating  a 
comparatively  high  humidity  for  all  of  the  districts,  and 
that  each  curve  bears  a  strong  resemblance  to  the  aver- 
age curve.  In  the  second  place,  the  periods  when  the  trans- 
piration was  excessive  were  few  and  short. 


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THE  EFFECT  OF  SOOT  ON  VEGETATION.  13 

By  referring  to  tlie  Annual  Meteorological  Summary 
of  Pittsburgh  we  find  that  the  annual  rainfall  has 
amounted  to  approximately  36  inches  during  the  year  and 
that  this  has  been  uniformly  distributed  throughout  the 
year,  and  has  not  varied  a  great  deal  from  year  to  year. 

In  like  manner,  the  monthly  temperature  reported 
shows  the  same  general  uniformity  as  the  other  records. 
Therefore  these  records  will  not  account  for  the  variations 
noted  below. 


THE   REGIONS   SELECTED. 

The  following  places  were  selected  in  Pittsburgh: 
(a)  Allegheny  Cemetery,  which  is  almost  in  the  center  of 
the,  town  and  nearly  surrounded  by  large  mills  which 
emit  considerable  quantities  of  smoke.  This  locality  was 
selected  because  it  was  believed  that  an  idea  could  be 
gleaned  concerning  the  effect  of  smoke  upon  introduced 
plants.  Here  no  special  injury  to  these  plants  was  noted, 
save  a  general  impoverished  condition,  (b)  Homewood 
Cemetery,  which  is  in  the  eastern  part  of  the  city  about 
midway  between  the  Allegheny  and  Monongahela  rivers 
and  almost  two  miles  from  any  large  mills.  Here  it  was 
found  that  native  conditions  were  fairly  well  maintained 
and  the  plants  presented  approximately  normal  condi- 
tions, (c)  Munhall  Run  is  located  where  the  smoke  has 
'been  spread  over  the  region  from  the  large  blast  furnaces 
and  steel  mills  in  Homestead  for  several  years.  Here  it 
was  found  that  the  vegetation  and  particularly  the  trees 
were  almost  entirely  killed  for  a  distance  of  almost  a  mile 
(Fig.  3).  Across  the  river  from  these  mills  and  near  the 
river  is  the  Baltimore  and  Ohio  Railroad,  the  smoke  from 
the  trains  of  which,  together  with  that  from  the  mills,  has 
killed  practically  all  the  trees  on  the  hillside  and  hilltop 
(Fig.  4).  Neither  of  these  places  enabled  one  to  fix  the 
cause  for  the  trouble  quite  so  well  as  that  of  Aliquippa 
and  the  nearby  vicinity,  about  twenty  miles  down  the 
Ohio  river  from  Pittsburgh.  By  referring  to  the  map 
the  topography  as  well  as  the  direction  of  the  prevailing 


14  THE  SMOKE  INVESTIGATION 

winds  may  be  understood  (Fig.  2).  The  particnlar 
regions  of  the  Aliquippa  district  to  which  attention  is  to 
be  directed  may  also  be  seen  by  referring  to  this  map. 
These  regions  were  selected  in  order  that  a  number  of 
different  conditions  might  be  secured.  They  were  as  fol- 
lows :  Region  1  is  on  the  spur  of  the  hill  extending  south- 
ward toward  the  mill  and  about  1500  feet  a  little  northwest 
of  the  mill.  Region  2  is  about  one-half  of  a  mile  north 
of  region  1  and,  on  account  of  the  prevailing  winds,  re- 
ceives very  little  smoke  and  fumes  from  the  mill.  Region 
3  is  approximately  900  feet  west  of  region  1.  Region  4 
is  about  1,300  feet  northwest  of  region  3  on  the  slope  of 
the  hill  and  seemed  to  be  well  protected  from  the  smoke 
and  fumes  from  the  mill.  Region  5  is  on  the  slope  of  the 
hill  near  the  Pittsburgh  &  Lake  Erie  Railroad  and  about 
1,500  feet  southwest  of  the  mill.  Region  6  is  in  the  valley 
near  the  mill  and  receives  the  full  effect  of  the  sraoke  and 
fumes.  The  mill  referred  to  is  Jones  and  Laughlin,  which 
has  been  established  there  since  1909. 

Besides  these  blast  furnaces,  there  are  railroads  on 
either  side  of  the  river  over  which  trains  run  at  frequent 
intervals.  The  prevailing  winds,  being  northwest,  are 
effective  in  carrying  smoke  and  gases  from  the  trains  and 
furnaces,  resulting  in  the  destruction  of  most  of  the  trees 
on  the  hillside  and  ravines  east  of  the  river.  On  the  west 
side  of  the  river  rather  extensive  observations  were  made 
in  the  regions  corresponding  approximately  to  the  numbers 
on  the  map  (Fig.  2).  In  these  regions,  studies  of  annual 
rings  and  of  the  anatomical  structure  of  leaves  were  made. 
Realizing  that  anything  which  would  cut  off  the  food 
making  in  the  plant  would  diminish  the  width  of  the  an- 
nual ring  and  that  this  might  be  produced  by  an  accidental 
breaking  of  a  limb  or  top  of  a  tree,  the  writer  took  cross  sec- 
tions of  the  stems  at  different  points,  as  Figs.  5-14  will 
show.  It  was  found  that  in  region  4  no  noticeable  injury 
could  be  detected  either  in  the  general  character  of  the  trees 
or  in  the  width  of  the  annual  rings.  The  difference  in  width 
of  annual  rings  was  found  to  be  well  marked  in  certain 


/^/y.  7.  Ulmus 


Fio  S    ULmus 

Plate  HL. 

PLATE    III. 
Fig.    7.      Cross   sections   of  an  Ulmus    (American   elm)    growing  on   the  campus 
at    State    College,    Pennsylvania,    showing    wide    and    rather    uniform    rings.      Here 
the    conditions    for    growth    are    favorable. 

Fig.  8.  Cross  sections  of  an  Ulmus  (American  elm)  growing  on  the  hillside 
at  Nine  Mile  Run  across  the  river  from  the  mills  at  Homestead.  Shows  a  de- 
cided   irregularity    in    the   character    of    the    annual    rings. 


fia.9    Locust 


^ia.  /O,  Hie  on  a 


PLeLteXZ, 


PLATE    IV. 

Fig.  9.  Cross  sections  of  a  Locust  growing  in  region  4  of  the  Aliquippa 
district,    sliowing    a    tendency    toward    a    narrowing    of    annual    rings. 

Fig.  10.  Cross  sections  of  a  Hicoria  growing  on  the  hilltop  near  Nine  Mile 
Run.  Shows  a  general  tendency  toward  narrow  annual  rings  on  account  of  the 
unfavorable  conditions  due   to   smoke  and   gases. 


fi^  //.   Hlcoria 


PLATE    V. 

Fig.  11.  Cross  sections  of  a  Hicoria  growing  on  the  hillside  near  region  3, 
Aliqulppa   district,   showing  a   narrowing   of  rings  during   the  past   three   years. 

Fig.  12.  Cross  sections  of  a  Hicoria  growing  in  the  mountains  near  State 
College,  Pennsylvania,  showing  wide  and  rather  uniform  annual  rings.  Here 
conditions    for    growth    are    favorable. 


fiq.  /3     Pin  us 


Fio.  /y.    P'l'rjUS 


Plate  JET 


PLATE    VI. 


Fig.  13.  Cross  sections  of  Pinus  strobus  (White  Pine)  growing  on  the  hilltop 
at  region  3,  Aliqulppa  district.  Shows  the  tendency  toward  the  narrowing  ol 
annual    rings. 

Fig.  14.  Cross  sections  of  Pinus  strobus  growing  on  the  mountains  near 
State  College,  Pennsylvania,  showing  wide  and  rather  uniform  annual  rings. 
Here    the    conditions    for    growth    were    favorable. 


16  THE  SMOKE  INVESTIGATION 

Elms  and  Pines.  The  sections  of  Elm  taken  at  region 
6  show  a  decided  narrowing  of  the  rings  for  the  last  three 
years  corresponding  with  the  time  that  the  mill  has  been 
established  in  the  neighborhood  (Fig.  5).  When  these 
sections  are  compared  with  sections  of  a  similar  tree  ob- 
tained at  State  College,  it  will  be  found  that  this  feature 
is  lacking  (Fig.  7)  ;  here  the  tree  was  in  a  favorable  place 
for  growth.  Fig.  6  illustrates  sections  of  an  Elm  obtained 
from  region  5,  Aliquippa  district,  which  show  evidence  of 
injury  due  for  the  most  part,  in  all  probability,  to  the 
smoke  and  gases  from  the  trains  which  run  at  frequent 
intervals.  Fig.  8  shows  sections  of  Elm  obtained  from 
the  hillside  at  Nine  Mile  Run  which  bear  evidence  of 
smoke  and  gas  injury.  This  is  shown  by  the  irregular 
and  narrow  annual  rings.  It  indicates,  furthermore,  that 
the  young  trees  are  injured  less  than  older  ones,  thus  ac- 
counting for  the  presence  of  a  number  of  scrubby  plants 
in  many  places. 

The  same  general  conditions  are  found  when  cross 
section  of  Hicoria  collected  at  region  3,  Aliquippa  dis- 
trict, are  compared  with  similar  ones  collected  at  Nine 
Mile  Run  and  on  the  mountains  near  State  College  (Figs. 
10,  11,  12). 

When  sections  of  pines  collected  from  region  3  are 
compared  with  similar  ones  collected  in  the  mountains 
near  State  College  it  will  be  found  that  this  narrowing 
of  annual  rings  is  present  in  the  former,  while  a  wide 
uniform  annual  ring  is  seen  in  the  latter  (Figs.  13,  14). 
A  locust,  which  is  commonly  thought  to  be  and  apparently 
is  sensitive  to  the  effects  of  smoke  and  gases,  found  grow- 
ing in  region  4,  bears  evidence  of  this  narrowing  of  an- 
nual rings  (Fig.  9).  Other  plants  in  this  region  did  not 
show  this  condition.  At  a  distance  of  1,500  feet  from 
the  mills  very  little  of  this  effect  could  be  observed  and 
is  explained  of  course  on  the  ground  that  the  winds  blow 
the  major  part  of  the  smoke  and  gases  away  from  the  sta- 
tions. A  large  number  of  wood  sections  were  examined 
and  Figs.  5-14  are  a  fair  representation  of  the  lot.  They, 
for  the  most  part,  tell  their  own  story. 


THE  EFFECT  OF  SOOT  ON  VEGETATION.  17 

AnotJier  common  condition  met  wherever  there  is 
smoke  and  gases  is  the  dying  of  the  leaves  from  the  tips 
down  (Fig.  16).  This  is  well  marked  in  the  rhododen- 
drons, pines  and  many  deciduous  trees.  The  leaves  of 
Gingko  in  the  Allegheny  Cemetery  were  found  not  only 
dying  at  the  tips  but  many  showed  dead  spots  in  the  leaves. 

Anatomical  study  of  leaves  collected  at  the  different 
stations  did  not  show  any  unusual  cork  formation  either 
in  the  blades  or  petioles.  In  certain  plants  (e.  g.,  the 
pines)  the  stomata  are  in  pits  which  might  be  expected 
to  be  filled  with  soot  held  there  by  tarry  substances.  Ex- 
amination and  comparison  of  leaves  collected  at  these  sta- 
tions, with  similar  leaves  collected  on  the  campus  in  State 
College  and  from  plants  experimented  with  in  the  nursery 
of  the  Department  of  Forestry,  Pennsylvania  State  Col- 
lege, do  not  show  any  marked  difference.  To  be  sure,  in 
each  instance  a  few  of  the  stomata  appeared  to  be  clogged, 
but  in  no  case  were  more  than  approximately  twenty-five 
per  cent,  found  in  this  condition. 

CONTROLLED  FIELD  EXPERIMENTS. 

In  order  to  determine  more  specifically  the  effect  of 
^oot  upon  plants,  controlled  field  experiments  were  per- 
formed in  the  following  manner.  Cases  of  the  sort  shown 
in  Fig.  17  were  placed  over  plants  of  suitable  size  and  in 
good  condition.  On  the  ground  within  each  case  and  on 
opposite  sides  of  the  plant  were  placed  two  crystalizing 
dishes  for  the  purpose  mentioned  below.  A  thermometer 
was  hung  in  each  case.  A  tin  tube  connected  at  one  end  with 
a  funnel  shaped  piece  was  passed  through  the  upper  cross- 
bar of  the  case.  This  funnel  shaped  piece  was  within 
the  case  and  was  turned  upward  at  an  angle  of  about  30°. 
On  the  same  tin  tube  and  outside  of  the  case  another  fun- 
nel shaped  piece  was  attached.  The  soot  was  applied  to 
the  plants  in  the  follo^'ing  manner :  small  quantities  were 
placed  in  the  funnel  on  the  outside  of  the  case  and  sub- 
sequently driven  into  the  case  by  means  of  a  small  stream 
of  air  entering  at  a  high  velocity.    By  this  means  the  soot 


18  THE  SMOKE  INVESTIGATION 

was  distributed  uniformly  over  the  plant.  To  determine 
the  amount  applied,  weighings  of  the  soot  collected  in  the 
crystalizing  dishes  were  made  and  these  computed  to 
unit  area.  The  soot  was  applied  at  daily  intervals  usually 
extending  over  about  one  week.  In  each  experiment  four 
cases  were  used,  one  as  a  control  and  three  for  the  applica- 
tion of  soot.  In  order  to  keep  down  the  temperature  in 
the  cases  they  were  protected  by  shades  of  cheese  cloth. 

ANALYSES  OF  SOOT  i. 

The  samples  of  soot  used  had  the  following  analyses  * : 

Tar  Ash        Fixed  Cai^bon 

'Sample  A.  6.12%  28.1%  05.78% 

Sample  B.  6.70%  5.5%  87.75% 

Sample  C.  1.12%  26.0%  72.88% 

EXPERIMENTS  IN  NURSERY  AND  GREENHOUSE. 

The  following  experiments  will  indicate  the  general 
results  obtained.  Care  was  taken  in  selecting  plants  which 
were  similar  and  in  good  condition  in  the  beginning  of 
each  experiment. 

Experiment  I. 

Begun  July  2,  1912.  Selected  Jack  Pine  seedlings  in 
the  (College  nursery.  Applied  small  quantities  of  soot  July 
2,  3,  4,  11,  12.  Continued  experiment  until  July  23.  Quan- 
tities of  soot  of  sample  A  used  as  follows :  In  case  No.  1, 
2.412  gm.  per  square  meter.  No.  2,  .438  gm.  per  square 
meter.    No.  3,  .438  gm.  per  square  meter.  No.  4,  Control  '. 


(1)  Volatile  matter  refers  to  that  portion  of  the  dried  sample 
which  was  driven  of?  by  heating  in  a  tightly  closed  platinum  crucible 
in  the  full  flame  of  a  Bunsen  burner  for  seven  minutes.  The  residue 
remaining  in  the  crucible  is  coke.  This  is  burned  by  heating  in  the 
air,  and  the  percentage  of  ash  is  determined.  The  percentage  of  coke 
minus  the  percentage  of  ash  gives  the  percentage  of  fixed  carbon. 

(2)  All  of  the  analyses  were  furnished  by  the  Industrial  Re- 
search Laboratory  of  the  University  of  Pittsburgh  and  were  made 
under  the  supervision  of  Dr.  R.  C.  Benner. 

(3)  Applications  of  .438  gm.  per  square  meter  is  sufficient  to 
make  a  continuous  black  coating  over  the  entire  plant. 


THE  EFFECT  OF  SOOT  ON  VEGETATION.  19 

At  end  of  time  all  plants  were  alive.  The  leaves  of 
the  plants  treated  displayed  a  tendency  to  drooping.  Many 
leaves  began  to  die  at  the  tips.  Those  near  the  ground 
were  completely  dead.  Old  leaves  seemed  to  suffer  most 
from  treatment.     The  control  remained  normal. 

Experiment  II. 

During  August,  1912,  under  similar  conditions  with 
the  same  kind  of  seedling  and  in  the  same  nursery.  The 
soot  applied  of  sample  B.  Quantities  of  soot  used  as  fol- 
lows: In  case  No.  1,  .219  gm.  per  square  meter.  No.  2, 
.219  gm.  per  square  meter.  No.  3,  .439  gm.  per  square 
meter.    No.  4,  Control. 

The  results  were  like  those  in  experiment  1. 

Experiment  III. 

During  March,  1913.  In  the  College  greenhouse. 
Potted  plants  of  tomato  used.  Other  conditions  similar 
to  the  above.  Soot  applied  of  Sample  C.  Quantities  ap- 
plied as  follows:  Case  No.  1,  7.2  gm.  per  square  meter. 
No.  2,  23.04  gm.  i>er  square  meter.  No.  3,  3.6  gm.  per 
square  meter.    No.  4,  Control. 

At  the  end  of  the  experiment  the  plants  exhibited  no 
differences  and  all  were  in  good  condition. 

Experiment  IV. 

Begun  July  21,  1913.  Selected  Jack  Pine  seedlings 
in  the  nursery  as  above.  Soot  applied  of  sample  C.  Ap- 
plied July  21,  22,  23,  24,  and  experiment  continued  until 
August  26,  1913.  The  following  quantities  of  soot  were 
used :  Case  No.  1,  23.4  gm.  per  square  meter.  No  2,  11.7 
gm.  per  square  meter.  No.  3,  12.96  gm.  per  square  meter 
No.  4,  Control. 

At  the  end  of  the  experiment  although  all  plants  were 
alive,  nevertheless  many  of  the  older  leaves  were  entirely 
killed  and  ready  to  fall  off.  The  younger  leaves  on  the 
whole  endured  the  treatment  better  than  the  older  ones. 


20  THE  SMOKE  INVESTIGATION 

Experiment  V. 

Begun  July  2,  1913.  Selected  Fir  plants  in  the  Col- 
lege nursery.  Applied  small  quantities  of  soot  every  other 
day  until  about  July  21,  1913.  Quantities  were  of  Sample 
C  The  following  amounts  were  used:  Case  No.  1,  3.78 
gm.  per  square  meter.  No.  2,  2.97  gm.  per  square  meter. 
No.  3,  3,6  gm.  per  square  meter.    No.  4,  Control. 

At  the  end  of  the  experiment  all  plants  seemed  to  be 
in  good  condition.  No  difference  could  be  seen  among 
them. 

EXPERIMENTS  WITH  PEA  SEEDLINGS. 

(a)  Samples  of  soil  taken  from  the  surface  and  at 
a  distance  of  two  inches  from  the  surface  from  near  the 
mills  at  Homestead  and  tested  for  the  presence  of  toxic 
gases  by  a  method  devised  by  Crocker,  Knight  and  Rose 
(8)  gave  negative  results. 

(b)  A  few  experiments  with  etiolated  seedlings  gave 
slightly  positive  results.  They  consisted  of  a  modified 
Crocker  type  as  follows :  A  can  of  50  liters'  capacity  was 
placed  over  the  etiolated  seedlings  and  sealed  around  the 
bottom  with  oiled  clay.  It  was  further  provided  with  an 
opening  through  the  upper  edge  which  permitted  the  ap- 
plication of  soot  to  the  seedlings.  At  right  angles  to  and 
below  this  opening  a  shaft  passed  through  the  can  and 
bore  a  fan  on  the  inside.  On  the  other  end  of  this  shaft 
was  a  pulley  to  which  a  motor  was  attached.  This  motor 
was  also  connected  with  a  blower  which  in  turn  was  con- 
nected to  the  can  by  means  of  a  rubber  and  tin  tube  ( Fig. 
16).  The  tin  tube  was  similar  to  the  one  used  in  the  field 
experiment.  The  soot  was  applied  by  placing  small  quanti- 
ties in  the  tin  tube.  It  was  then  forced  and  distributed 
into  the  case  by  running  the  blower  at  high  speed  simul- 
taneously with  the  rotation  of  the  fan. 

These  experiments  were  repeated  a  number  of  times 
with  similar  outcome  so  that  one  experiment  will  suffice 
to  illustrate  the  character  of  the  results  olbtained.  Etio- 
lated seedlings  of  sweet  pea  grown  on  moist  cotton  were 
used.    After  they  had  grown  2  to  3  cm.  they  were  placed 


THE  EFFECT  OF  SOOT  ON  VEGETATION.  21 

under  a  dark  chamber  sealed  around  the  bottom  with  oiled 
clay.  Daily  applications  of  soot  were  made  for  seven  days. 
At  the  end  of  two  weeks  observations  were  made.  Quanti- 
ties of  soot  used  of  Sample  C  were  as  follows:  Case  No. 
1,  3.78  gm.  per  square  meter.  No.  2,  2.97  gm.  per  square 
meter.  No.  3,  3.24  gm.  per  square  meter.  No.  4,  Control. 
At  the  end  of  the  experiment  the  only  visible  difference 
was  an  apparent  checking  of  growth  in  the  case  of  the 
plants  treated  with  soot.  This  condition  became  more  ap- 
parent when  the  plants  thus  treated  were  allowed  to  grow 
in  the  open  for  a  few  days. 

SOOT  FALL  FOR  WOODLAWN. 
In  addition  to  other  data  obtained  open  glass  jars 
twelve  inches  deep  and  four  inches  in  diameter  were  placed 
at  each  station  under  observation  and  analysis  made  of 
the  matter  collected  in  each  jar  placed  in  the  region  of 
Woodlawn,  Similar  records  were  made  for  various  sta- 
tions in  Pittsburgh  and  are  given  in  another  report  of  this 
investigation. 

Station  at  3. 
Total  deposit  for  4  months,  June,  July,  August  and 
September,  1912,  was  1.1442  grams — 93  tons  per  square 
mile  per  year. 

Analysis. 
Tar,  1.86% 

Fixed  carbons,         28.34% 
Ash,  68.8  % 

Iron  in  ash,  12.7  %     Fe203. 

Station  at  5. 
'Samples  taken  July,  June  and  October,  1912.    Other 
samples  not  good  (contained  leaves  and  bugs) . 

Total  weight  of  solids — 6.6250   grams — 68   tons   per 
square  mile  per  year. 

Analysis. 
Tar,  6.5% 

Fixed  carbons,  41.1% 

Ash,  51.4% 

Iron  in  ash,  8.3%     FeaOs. 


22  THE  SMOKE  INVESTIGATION 


General  Considerations 

It  follows  from  the  above  data  that  injury  to  vegeta- 
tion is  caused  by  the  smoke  and  gases  given  off  by  indus- 
trial establishments.  In  many  instances  the  injury,  and 
sometimes  the  complete  destruction  of  the  vegetation,  can 
be  traced  directly  to  smoke  and  gases  accompanying  the 
smoke.  In  this  particular  all  investigators  agree.  But 
this  alone  does  not  give  much  insight  as  to  the  specific 
cause  or  causes  for  the  injury.  It  has  been  determined 
that  smokes  vary  widely  in  composition  both  quantita- 
tively and  qualitatively,  and  that  several  gases  may  be 
variously  associated  with  each  other  and  with  the  solids 
present.  This  being  the  case  the  proiblem  then  is  to  de- 
termine the  extent  of  the  injury  of  the  several  substances. 
On  account  of  the  different  compositions  of  smokes  in  dif- 
ferent localities  the  problem  is  a  complex  one,  one  which 
at  the  present  moment  is  only  partly  solved.  Many  valu- 
able data  have  been  obtained,  but  for  the  most  part  from 
the  study  of  the  gases  occurring  with  the  smoke  and  only 
to  a  slight  extent  with  reference  to  its  siolid  components. 
The  writer  has  undertaken  to  determine  the  extent  of  the 
injury  to  plants  caused  by  the  soot,  i.  e.,  by  the  "fixed 
carbon"  as  elsewhere  defined  and  as  supplied  the  writer 
for  this  investigation  by  Dr.  R.  C.  Benner.  It  is  the  opin- 
ion of  the  writer  that  the  final  word  has  not  been  said  in 
this  regard. 

The  objection  may  'be  raised  that  the  effect  of  a  small 
amount  of  soot  applied  over  a  long  period  will  not  be 
the  same  as  when  applied  in  large  amounts  during  a 
shorter  period,  the  conditions  namely  of  the  experiments. 
This  objection  may  be  well  taken,  but  the  writer  thinks 
it  not  unlikely  that  there  is  less  weight  to  be  attached  to 
it  than  at  first  sight  appears.  The  conditions  of 
the  experimentation  were,  however,  unavoidable,  and 
the  conclusion  must  rest  on  the  probability  that  the  larger 


Fiq.  /5  Leaves  o-f  Rhododendron 


"f 


F^lQ-  f^'  L.a.boratoriJ   AppayaTus 

Piateinj. 

PLATE    VII. 

Fig.  15.  Leaves  of  Rhododendron  growing  at  region  1,  Aliquippa  district, 
showing   how    the    leaves    die   from    the    tips    back. 

Fig.  16.  Shows  a  view  of  the  apparatus  used  in  the  laboratory  to  experi- 
ment   with    etiolated    seedlings. 


^ 


\ 


F^ia   /7.    Field   Ajbjbaratus . 

Plate m 

PLATE     VIII. 
Fig.    17.     A    view    of    the    apparatus    used    in    the    field    experiments,    showing 
the    method    of    treating    plants    with    soot.      The    glass    case    is    on    the    left    and 
the   pressure    tank    is   on   the   right. 


THE  EFFECT  OF  SOOT  ON  VEGETATION.  23 

amounts  lof  soot  used  did  in  large  measure  compensate  for 
the  shorter  periods  of  exposure.  In  the  determined  soot 
fall,  computed  for  one  year,  it  was  found  that  the  tar  and 
"fixed  carbon"  amounted  to  10.8  gm.  per  square  meter  in 
one  instance  and  11.52  gm.  per  square  meter  in  the  other. 
In  the  experiments  tar  and  "fixed  carbon"  were  used  in 
amounts  varying  from  .21  gm.  to  17.  gm.  per  square  meter. 
The  amounts  of  soot  generally  used  in  the  experiments 
were  therefore  aTx>ut  equivalent  to  an  entire  year's  soot 
fall,  and  in  consequence  may  be  regarded  as  more  toxic 
because  ( 1 )  under  experimental  conditions  the  soot  falling 
on  the  plants  was  more  likely  to  remain,  wind  and  rain 
being  absent,  and  because  (2)  the  amount  used  fell  on  the 
plants  in  a  much  shorter  period  of  time.  In  each  instance 
the  plants  were  completely  covered  with  soot  during  the 
experiments.  Therefore,  it  appears  that  so  far  as  the 
amount  of  soot  is  concerned,  the  obtaining  of  equivalent 
conditions  has  been  approximately  secured. 

It  may  be  maintained  that  the  injury  is  purely  or 
partly  a  mechanical  one  brought  about  by  the  plugging 
of  the  stomata,  the  plant  consequently  suffering  from  the 
suppression  of  the  free  exchange  of  gases.  But  inasmuch 
as  a  very  small  percentage  of  the  stomata  in  the  leaves 
collected  in  the  field  and  from  the  plants  experimented 
with  in  the  nursery  were  found  to  be  clogged,  this  opinion 
finds  little  or  no  support.  Nor  did  soots  of  varying  per- 
centages of  tar  and  "fixed  carbon"  display  any  differences 
in  this  respect. 

In  localities  where  smoke  and  gases  are  a  nuisance 
there  is  a  general  though  vague  impression  that  soot  and 
tars  are  toxic  or  otherwise  injurious  to  plants.  If  this 
be  the  case,  the  writer  would  have  expected  to  have  ob- 
tained much  more  pronounced  results  in  the  above  experi- 
ments, that  is  to  say  with  solids  and  semi-solids.  The  ques- 
tion of  the  effect  of  gases  has  not  been  considered  in  this 
paper. 


24  THE  SMOKE  INVESTIGATION 


Conclusions 

1.  It  is  a  matter  of  general  opinion  that  smoke  from 
mills  injures  nearby  vegetation.  That  this  opinion  is  jus- 
tified is  evidenced  not  only  by  the  general  external  appear- 
ance of  many  of  the  constituent  plants,  but  also  by  their 
internal  appearance,  as  shown  by  the  size  of  annual  rings 
and  by  lesions  in  leaves. 

2.  The  experiments  described  in  this  paper  show  that, 
especially  in  the  case  of  pines,  when  soot  is  applied  in 
small  quantities  over  a  considerable  interval  of  time,  meas- 
urable injury  follows.  Soot  is  therefore  poisonous  to 
vegetation. 

3.  Soot  is  a  mixture  of  pure,  finely  divided  carbon, 
ash,  tar  and  gases.  Since,  however,  pure  carbon  can  not 
be  regarded  as  poisonous,  its  effect  on  plants,  if  indeed  it 
has  any,  must  be  charged  to  the  mechanical  clogging 
of  stomata,  or  to  the  ash,  which  may,  in  the  presence 
of  water  (rain)  provide  solutions  injurious  to  leaves. 
Aside  from  this  latter  possibility,  which  has  not  been  in- 
vestigated in  this  study,  actual  observation  reveals  the 
fact,  that  only  a  small  percentage  of  the  stomata  were 
clogged,  from  which  it  is  inferred  that  little  or  no  inter- 
ference with  interchange  of  gases  occurs.  It  is  true  that 
a  certain  number  had  the  appearance  of  being  clogged, 
nevertheless  it  is  doubtful,  in  the  opinion  of  the  writer, 
that  there  was  an  efficient  hindrance  to  the  diffusion  of 
gases  in  view  of  the  studies  of  Brown  and  Escombe  (1) 
and  Lloyd  ( 12 ) .  It  is  of  course  obvious  from  results  of  such 
studies  that  the  effect  of  the  interference  by  small  particles 
on  diffusion  through  a  minute  opening  can  not  be  inferred 
but  must  be  made  the  subject  of  specific  investigation. 

4.  The  injury  done  by  the  soot  of  smoke  to  vegeta- 
tion, is  therefore,  probably  due  chiefly,  if  not  entirely,  to 
the  accompaning  ash,  tar  and  gases. 


THE  EFFECT  OF  SOOT  ON  VEGETATION.  25 

5.  It  is  a  well  established  fact,  based  upon  results 
of  other  studies,  that  fumes  containing  sulphur  dioxide  and 
sulphur  trioxide  do  considerable  injury  to  vegetation.  It 
is  also  known  that  the  gases,  ethylene,  a  constituent  of  il- 
luminating gas;  carbon  monoxide,  benzene,  hydrogen  sul- 
phide, and  carbon  bisulphide  are  injurious  to  plants. 


26  THE  SMOKE  INVESTIGATION 


Bibliography  of  References  Cited  in  Text 

1.  Brown,  H.  T.,  and  Escombe,  F.  Static  diffusion  of  gases.  Phil. 
Trans.  Roy.  Soc.  London.  B.  193:  233-291.     1900. 

2.  Buckhout,  W.  A.  The  effect  of  gases  and  smoke  on  vegetation. 
Ann.  Report  of  Agr.  for  Penn.    164-192.     1900. 

3.  Cohen,  J.  B.,  and  Ruston,  A.  G.  Smoke,  a  study  of  town  air. 
pp.  1-88.     Edward  Arnold,  London,  1912. 

4.  Crocker,  Wm.,  and  Knight,  L.  Effect  of  illuminating  gas  and 
ethylene  upon  flowering  carnations.     Bot.  Gaz.  46:  259-276.    1908. 

5.  Crothers,  C,  and  Ruston,  A.  G.  Effect  of  atmospheric  impurities 
near  a  large  city.    Jour.  Agr.  Sci.  4:  25-55.     1911. 

6.  Gatin,  C.  L.  Die  gegen  die  Abnutzung  und  den  Staub  der 
Strassen  angewendenen  Verfahren  und  ihre  Wirkung  auf  die  Veg- 
etation.   Zeitschr.  Pflanzenkrank.    22:  193-204.     1912. 

7.  ,  Le  goudronnage  des  routes  et  sou  action  sur  la  vegeta- 
tion avoisiante.     Ann.  Sci.  Nat.  Bot.  15:  165-252.     1912. 

8.  Haywood,  J.  K.  Injury  to  vegetation  by  smelter  fumes.  Bull. 
Bur.  of  Chem.  U.  S.  Dept.  of  Agr.  89.     1905. 

9.  ivnight,  L.  I.,  and  Crocker,  Wm.  Toxicity  of  smoke.  Bot.  Gaz. 
55:  337-371.    1913. 

10.    ,   Rose,    R.   C,   and   Crocker,   Wm.     A   new   method   of 

detecting  traces  of  illuminating  gas.    Science  N.  S.  31 :  636.    1910. 

11.     ,    Effect    of    various    gases    and    vapors    upon    etiolated 

seedlings  of  the  sweet  pea.     Science  N.  S.    31:  635-636.     1910. 

12.  Lloyd,  F.  E.  The  physiology  of  stomata.  Carn.  Inst.  Wash. 
Pub.  82.     1908. 

13.  Molisch,  H.  Uber  den  Einfiuss  des  Tabakrauches  auf  die  Pflanze. 
Teil  I.  Sitzgber.  Kais  Akad.  (Wein)  Math.  Nat.  Kl.  120:  3-30. 
1911. 

14.    .    t)ber  den  Einfiuss  des  Tabakrauches  auf  die  Pfianze. 

Teil  II.    Op.  cit.  120:  813-838.     1911. 

15.  Parish,  S.  B.  The  effect  of  cement  dust  on  citrus  trees.  Plant 
World  13:  288-291. 

16.  Peirce,  Geo.  J.  On  effect  of  cement  dust  on  orange  trees.  Plant 
World  13:  283-288. 

17.  Ruston,  A.  G.  Effects  of  smoke  on  vegetation.  Report  of  Smoke 
Abatement  League  of  Great  Britain:  44-53.     1911. 

18.  Widtsoe,  John  A.  Relation  of  smelter  smoke  to  Utah  agricul- 
ture.   Agr.  Bull.  Utah  Agr.  Exp.  Sta.  8.     1903. 


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